Single-carrier Block Transmission Research Articles

Ordered Block Detector for Single-Carrier Generalized Spatial Modulation in Frequency-Selective Fading Channels

In this letter, we present a detection algorithm for single-carrier generalized spatial modulation in frequency-selective fading channels. We extend the ordered-block minimum mean square error (OB-MMSE) detector, originally conceived for flat fading channels, to frequency-selective fading channels by exploiting the format of unique word-based single-carrier block transmission and incorporating decision feedback. Moreover, a frequency-domain prefilter is used to ameliorate error propagation and simplify the operation of OB-MMSE detector. Simulation results show the efficacy of the proposed algorithm.

32kbps terrestrial acoustic communications of single carrier block transmission employing transmit precoding and channel interpolation

32kbps terrestrial acoustic communications of single carrier block transmission employing transmit precoding and channel interpolation

Performance Analysis of OCDM for Wireless Communications

Orthogonal chirp division multiplexing (OCDM) was recently introduced as a new multi-carrier scheme based on the chirp spread spectrum (CSS) and shown to be more robust to interference caused by insufficient guard intervals. However, a thorough analysis of OCDM for wireless channels has not been conducted. Thus, this paper investigates the performance of OCDM affected by different impairments that are typical in a wireless channel and shows that uncoded OCDM performs better than OFDM and similar to single carrier block transmissions in multipath channels. Building on previous results, this study also shows that OCDM is more robust to time-burst interference (TBI) than its competitors and to narrow band interference (NBI) than OFDM because of spreading. However, OCDM is shown to suffer because of the loss of orthogonality caused by carrier frequency offset (CFO) and is analytically shown to have the same peak-to-average power ratio (PAPR) as OFDM.

Hybrid-Domain Parallel Decision Feedback Equalization for Single-Carrier Block Transmission

To combat intersymbol interference (ISI) in single-carrier block transmission systems, the hybrid decision feedback equalizer (HDFE) is a low-complexity, symbol-by-symbol detector that combines a frequency-domain feedforward filter and a time-domain feedback filter. To mitigate the error propagation effect of HDFE while preserving the implementation advantages of frequency-domain equalization, we propose the parallel HDFE (P-HDFE) algorithm that operates, based on the reliability of the decision variable, as an ordinary HDFE or a sequence detector that consists of multiple HDFEs running in parallel. Our study shows that, at moderate to high signal-to-noise ratios (SNRs), P-HDFE outperforms HDFE with little increase in complexity. We analyze the symbol error rate of P-HDFE at high SNRs for the case of quaternary phase-shift keying and static ISI channels, accounting for error propagation and residual ISI. Simulations demonstrate the accuracy of the analysis.

Single-Carrier Frequency-Domain Equalization With Hybrid Decision Feedback Equalizer for Hammerstein Channels Containing Nonlinear Transmit Amplifier

We propose a nonlinear hybrid decision feedback equalizer (NHDFE) for single-carrier (SC) block transmission systems with nonlinear transmit high power amplifier (HPA), which significantly outperforms our previous nonlinear SC frequency-domain equalization (NFDE) design. To obtain the coefficients of the channel impulse response (CIR) as well as to estimate the nonlinear mapping and the inverse nonlinear mapping of the HPA, we adopt a complex-valued (CV) B-spline neural network approach. Specifically, we use a CV B-spline neural network to model the nonlinear HPA, and we develop an efficient alternating least squares scheme for estimating the parameters of the Hammerstein channel, including both the CIR coefficients and the parameters of the CV B-spline model. We also adopt another CV B-spline neural network to model the inversion of the nonlinear HPA, and the parameters of this inverting B-spline model can be estimated using the least squares algorithm based on the pseudo training data obtained as a natural byproduct of the Hammerstein channel identification. The effectiveness of our NHDFE design is demonstrated in a simulation study, which shows that the NHDFE achieves a signal-to-noise ratio gain of 4dB over the NFDE at the bit error rate level of $10^{-4}$ .

Performance evaluation of intra-vehicle wireless sensor network systems

Intra-vehicle wireless sensor networks (IVWSNs) enable sensor technologies to be integrated into vehicles and provide part-cost, assembly, and maintenance savings, as well as fuel efficiency through the elimination of wires. Ultra-wide band (UWB) communication is considered a competitive candidate for IVWSNs. Extensive analysis has been done for indoor and outdoor propagation, but the analysis of IVWSNs environments has rarely been studied. In this paper, the error-rate performance of UWB propagation for these IVWSNs is investigated and compared under different transmission schemes. And we also study the effects of some parameters on communication performance, such as the number of rake fingers and direct sequence spread factor of an impulse radio system, the cyclic prefix size of a single carrier block transmission with frequency domain equalisation system, and the delay line time of a transmitted reference pulse cluster autocorrelation receiver. Study results offer valuable insight for the realistic IVWSNs.

Asymptotically Optimal Low-Complexity SC-FDE With Noise Prediction in Data-Like Improper-Complex Interference

In this paper, single-carrier (SC) block transmission of improper-complex data symbols is considered over a multiple-input multiple-output (MIMO) frequency-selective channel with data-like cochannel interference (CCI). To exploit the cyclostationarity and impropriety of the desired and the interfering signals, an equalizer is designed that oversamples the received signal and then processes the sampled block by using widely-linear (WL) feedforward (FF) and noise-predicting feedback (NP-FB) filters. For the given equalizer structure, the minimum mean-squared error (MMSE)-optimal WL FF and NP-FB filters have high computational complexity due to the augmented correlation matrix of the data-like CCI in the received signal. Motivated by the asymptotic property of the correlation matrix, we approximate in the frequency domain the matrix by a block matrix with diagonal blocks. This leads to the low-complexity WL design of a frequency-domain FF filter and a causally noise-predicting FB filter. It is shown that this MIMO SC frequency-domain equalizer with noise prediction is asymptotically optimal in the sense that the average mean-squared error converges to that of the MMSE-optimal equalizer as the block length tends to infinity. Numerical results show that the proposed equalizer performs well even with a moderate block length.

阈值判决引导的单载波分块传输稀疏信道估计

阈值判决引导的单载波分块传输稀疏信道估计

Hybrid-Domain Sequence Detector for Training Sequence-Aided Single-Carrier Block Transmission Signals

Combating the intersymbol interference is an important issue in single-carrier block transmission systems. To exploit the advantages of frequency-domain (FD) processing, we propose in this paper a hybrid-domain sequence detector that combines FD prefiltering with time-domain tree search detection. The proposed algorithm achieves a detection performance that is very close to that of the conventional tree search equalizers (which employ the QRD-M or sphere decoding algorithm), but with a much lower complexity. In addition, the proposed algorithm performs significantly better than the decision-feedback equalizer, with only a modest increase in complexity.

Multi-channel iterative FDE for single carrier block transmission over underwater acoustic channels

Recently, single carrier block transmission (SCBT) has received much attention in high-rate phase-coherent underwater acoustic communication. However, minimum-mean-square-error (MMSE) linear FDE may suffer performance loss in the severely time dispersive underwater acoustic channel. To combat the channel distortion, a novel multi-channel receiver with maximum ratio combining and a low complex T/4 fractional iterative frequency domain equalization (FDE) is investigated to improve diversity gain and the bit error rate (BER) performance. The proposed method has been verified by the real data from a lake underwater acoustic communication test in November 2011. At 1.8 km, the useful data rates are around 1500 and 3000 bits/ s for BPSK and QPSK respectively. The results show the improvements of system performance. Compared with MMSE FDE system, the output SNR improvement is 6.9 dB, and the BER is from 10-3 to no error bits for BPSK. The output SNR improvement is 5.3 dB, and the BER is from 1.91×10-2 to 2.2×10-4 for QPSK.

Single-Carrier Frequency-Domain Equalizer with Multi-Antenna Transmit Diversity

Single-carrier (SC) block transmission with cyclic prefix (CP) is a method with several advantages that has been incorporated into standards. This paper has analyzed the performance of multi-antenna SC-FDE under Alamouti signaling and cyclic-delay diversity (CDD). Our analysis shows that the characteristic of diversity it is depends on data block length and data transmission rate as well as on the channel memory and antenna configuration. At higher rates their diversity diminishes and full diversity is available to both CDD and Alamouti signalling below a certain rate threshold. From our investigation we say that at high rates Alamouti signalling provides twice the diversity of SISO SC-FDE, while the diversity of the SISO SC-FDE under the CDD diversity degenerates. In this paper, we analyze the performance of SC-FDE in conjunction with either cyclic delay diversity (CDD) or Alamouti signaling, fully characterizing the diversity as a function of transmission-block length, number of antennas data rate and channel memory. In the process, we obtain a threshold rate (as a function of data-block length, channel memory, and number of antennas) below which the full spatial-temporal diversity is achieved, while at higher rates the diversity of both schemes diminishes. Our analysis shows that at high rates Alamouti signaling provides twice the diversity of SISO SCFDE, while the CDD diversity degenerates to the diversity of the SISO SC-FDE.

A reduced-complexity near-ML detection for broadband single-carrier transmission

In our recently proposed reduced-complexity near-maximum likelihood block signal detection employing QR decomposition and Malgorithm (QRM-MLBD) for broadband single-carrier (SC) block transmission, unreliable symbol candidates are removed from the symbol tree based on the hard-decision minimum mean square error based frequencydomain equalization (MMSE-FDE). In this paper, to further remove the unreliable symbol candidates and consequently reduce the computational complexity, we introduce a soft-decision MMSE-FDE based selection of reliable symbol candidates into reduced-complexity QRM-MLBD. It is shown that the soft-decision MMSE-FDE based selection significantly reduces the computational complexity while achieving a bit error rate (BER) performance similar to the original QRM-MLBD.

A Two-Stage Approach for the Estimation of Doubly Spread Acoustic Channels

In this paper, the estimation of doubly spread acoustic channels is investigated. By parameterizing the amplitude variation and delay variation of each path with polynomial approximation, this paper derives a mathematical model for the discrete-time channel input–output relationship tailored to single-carrier block transmissions. Based on the mathematical model, the channel estimation problem is transformed into estimation of the low-dimensional parameter sets (amplitude, delay, Doppler scale) that characterize the channel. A two-stage sparse channel estimation technique is then developed, which estimates the delay and Doppler scale sequentially. Compared to the one-stage joint estimation, the two-stage estimation approach greatly reduces the number of candidates on the delay-Doppler scale grid searched by the orthogonal matching pursuit (OMP) algorithm, that is, the dictionary size is reduced dramatically. As a result, the computational complexity is much lower. Further, the two-stage approach demonstrated higher levels of accuracy in computer simulations and led to better detection performance when applied to experimental data.

Single-Carrier Frequency Domain Equalization for Hammerstein Communication Systems Using Complex-Valued Neural Networks

Single-carrier (SC) block transmission with frequency-domain equalization (FDE) offers a viable transmission technology for combating the adverse effects of long dispersive channels encountered in high-rate broadband wireless communication systems. However, for high-bandwidth-efficiency and high-power-efficiency systems, the channel can generally be modeled by the Hammerstein system, which includes the nonlinear distortion effects of the high-power amplifier (HPA) at transmitter. For such nonlinear Hammerstein channels, the standard SC-FDE scheme no longer works. This paper advocates a complex-valued (CV) B-spline neural-network-based nonlinear SC-FDE scheme for Hammerstein channels. Specifically, we model the nonlinear HPA, which represents the CV static nonlinearity of the Hammerstein channel, by a CV B-spline neural network, and we develop two efficient alternating least squares schemes for estimating the parameters of the Hammerstein channel, including both the channel impulse response coefficients and the parameters of the CV B-spline model. We also use another CV B-spline neural network to model the inversion of the nonlinear HPA, and the parameters of this inverting B-spline model can easily be estimated using the standard least-squares algorithm based on the pseudo training data obtained as a natural byproduct of the Hammerstein channel identification. Equalization of the SC Hammerstein channel can then be accomplished by the usual one-tap linear equalization in the frequency domain as well as the inverse B-spline neural network model obtained in the time domain. Extensive simulation results are included to demonstrate the effectiveness of our nonlinear SC-FDE scheme for Hammerstein channels.

Low complexity timing estimation and resynchronization for asynchronous bidirectional communications with multiple antenna relay

SummaryIn this paper, we consider an asynchronous bidirectional communication system over flat fading channels in which the two source nodes are not perfectly synchronized. A low complexity pilot aided timing estimation and resynchronization scheme is proposed to combat the fractional asynchronous delay between the two source nodes. In the proposed scheme, cyclic prefixed single carrier block transmission is implemented at the two sources and frequency domain orthogonal pilots are transmitted to the relay simultaneously. After timing and channel estimation at the relay, a fractionally spaced frequency domain equalizer is employed at the relay to resynchronize the received mixed signals. With the proposed resynchronization scheme, the data detection at the two sources is the same as in a perfect synchronized system, because the two asynchronous signals are already resynchronized at the relay node. Simulation results show that the performance gap between the proposed scheme and the perfect synchronized system is within 1 dB when there are four antennas at the relay. Copyright © 2014 John Wiley & Sons, Ltd.

Receiver Design for Single-Carrier Block Transmission Over Doubly Selective Channels

Single-carrier block transmission is an alternative scheme to orthogonal frequency-division multiplexing (OFDM) for wireless broadband communications. In this paper, a receiver is designed for sing...

Two time slots distributed time‐reversal space‐time block coding for single‐carrier block transmissions

Distributed space-time block coding (STBC) is a promising technique for future broadband wireless communication system, because of its substantially improving the reliability of wireless channel by exploiting cooperative spatial diversity. In this study, the authors propose a novel two time slots distributed time-reversal STBC scheme for amplify-and-forward relay-assisted single-carrier (SC) block transmissions over frequency-selective fading channel. They first exploit the discrete Fourier transform extended properties to construct a linear precoding matrix. They then employ a low-complexity suboptimal frequency domain decision feedback equalisation (FD-DFE) to collect potential multipath diversity at high signal-to-noise ratio. Simulation results demonstrate that the proposed scheme provides better performance than the conventional distributed SC-STBC scheme with minimum-mean-square error FD linear equalisation.

Low‐complexity time‐domain linear equaliser for single‐carrier block transmissions

Traditionally, frequency-domain equalisers have been used to equalise the single-carrier block transmission (SCBT) signals. However, to support the frequency-domain equaliser, two fast Fourier transform modules are required, which will increase the circuit complexity and chip area. A low-complexity time-domain linear equaliser for SCBT is proposed, which is less complicated than conventional frequency-domain equalisers, at the expense of an acceptable degradation in performance. For instance, for 60 GHz conference room non-line-of-sight channels, the complexity can be reduced by half at the expense of a 1.5 dB performance loss.

A Novel Subblock-Based Frequency-Domain Equalizer over Doubly-Selective Channels

A novel frequency-domain equalizer (FDE) is proposed for single-carrier block transmission over a doubly-selective channel. The proposed FDE partitions a received block into multiple subblocks in order to reduce the effect of the time variation of the channel. The nonuniformity in the error statistics of a subblock-based FDE is analyzed, when a one-tap minimum mean-squared error (MMSE) equalizer is employed. The nonuniformity is exploited to remove the drawback of subblock processing so that the performance of a subblock-based FDE is significantly improved. Numerical results show that the proposed FDE has much better performance than other known subblock-based FDEs. Furthermore, it has robust performance over high Doppler environments.

Frequency Domain DFE for Single-Carrier STBC Block Transmission

Space-time block coding (STBC) is a novel transmit diversity technique that can substantially improve the reliability of wireless communication channel. In this letter, we investigate single-carrier STBC block transmission over frequency-selective fading channel. Based on the minimum mean square error (MMSE) criterion, by exploiting the reliability of tentative decision symbols, we propose a novel suboptimal, low complexity frequency domain decision feedback equalization (FD-DFE) scheme for SC STBC. Simulation results show that the proposed scheme provides better performance than the conventional scheme.